1. Field of the Invention
The invention relates to the fields of immunology and molecular biology.
2. Related Art
Avian pneumovirus (APV), also known as turkey rhinotracheitis virus, was first reported in South Africa in 1978 (Buys & Du Preez, Turkeys 28:36 (1980)) and, subsequently, was isolated in Europe, Israel and Asia (Alexander, in Barnes et al., eds., Diseases of Poultry, Iowa State University Press, Ames, Iowa (1997), pp. 541-569; Cavanagh and Barett, Virus Res. 11:241-256 (1988); Jones et al., Vet. Rec. 119:599-600 (1986); McDougall and Cook, Vet. Rec. 118:206-207 (1986); Wilding et al., Vet. Rec. 118:735 (1986)). The United States was considered free of APV until 1996, when it was isolated for the first time in Colorado from an outbreak of upper respiratory tract disease in turkeys (Cook et al., Avian Pathol. 28:607-617 (1999); Kleven, in Proceedings of the U.S. Animal Health Association 101st Annual Meeting, U.S. Animal Health Association, Washington, D.C. Report of the Committee: transmissible diseases of poultry and other avian species (1997), pp. 486-491). This first isolate was called APV/Colorado (APV/CO). Subsequently, APV infection was reported in turkeys in Minnesota, from which the virus has spread to the neighboring states of North and South Dakota (Goyal et al., North Central Avian Disease Conference, Minneapolis, Minn. (October, 1999); Panigrahy et al., Avian Dis. 44:17-22 (2000)). APV has emerged as a major problem for turkey industries in Minnesota. In 1999, 37% of the turkey flocks in Minnesota were positive for APV antibodies, causing economic losses of approximately $15 million per year (Gulati et al., J. Clin. Microbiol. 38:4010-4014 (2000)).
APV belongs to the genus Metapneumovirus within the subfamily Pneumovirinae of the family Paramyxoviridae (Pringle, Arch. Virol. 143:1449-1459 (1998)). The genome of Metapneumovirus is a non-segmented, single-stranded, negative-sense RNA with a gene order of 3′-Leader-N-P-M-F-M2-SH-G-L-Trailer-5′. APV was assigned to a new genus because its genome contains eight genes arranged in a different order from the ten genes of members of genus Pneumovirus, such as respiratory syncytial virus (RSV) (Collins et al., “Parainfluenza viruses,” in Fields Virology, Fields et al., eds., Lippincott-Raven, Philadelphia, Pa. (1996), pp. 1205-1241; Ling et al., J. Gen. Virol. 73:1709-1715 (1992); Randhawa et al., J. Virol. 71:9849-9854 (1997)). The newly discovered human metapneumovirus (hMPV) is the only mammalian virus that has been included tentatively in the genus Metapneumovirus (Van den Hoogen et al., Nat. Med. 7:719-724 (2001); Van den Hoogen, et al., Virology 295:119-132 (2002); Njenga et al., Virus Res. 91:163-169 (2003)).
On the basis of level of genetic variation in the attachment (G) protein, European APV isolates have been divided into two subgroups, designated A and B (Juhasz and Easton, J. Gen Virol. 75:2873-2880 (1994)). These two subgroups were also shown to be antigenically distinct (Bayon-Auboyer et al., Arch. Virol. 144:1091-1109 (1999)). Until late 1996, all known APV isolates belonged to either the A or the B subgroup. Surprisingly, the APV isolates from the U.S. were shown to cross-neutralize poorly with European subgroup A and B viruses, suggesting that they belong to a different subgroup. A new subgroup, C, has been proposed for the U.S. isolates of APV (Cook et al., Avian Pathol. 28:607-617 (1998); Kleven, in Proceedings of the U.S. Animal Health Association 101st Annual Meeting, U.S. Animal Health Association, Washington, D.C. Report of the Committee: transmissible diseases of poultry and other avian species (1997), pp. 486-491; Seal, Virus Res. 58:45-52 (1998); Seal, Health Res. Rev. 1:67-72 (2000); Shin et al., J. Clin. Microbiol. 40:1687-1693 (2002)). Recently, a subgroup D strain of APV has been reported (Bayon-Auboyer et al., J. Gen. Virol. 81:2723-2733 (2000)). The U.S. isolates have been shown to be different from Subgroup D strains (Toquin et al., Avian Dis. 44:977-982 (2000)).
The nucleotide sequences of all the eight mRNAs of APV subgroup A have been reported (Randhawa et al., J. Virol. 71:9849-9854 (1997) and references therein). However, the nucleotide and deduced amino acid sequences of only N, P, M, F and M2 genes of APV/CO have been reported (Dar et al., Virus Res. 79 (1-2):15-25 (2001); Seal, Virus Res. 58:45-52 (1998); Seal et al., Virus Res. 66:139-147 (2000); Genbank accession—AF176592).
At present, there is no satisfactory vaccine available for APV and also no method available to genetically manipulate the genome of APV.